Various arrangements for countercurrent chromatography have been developed to produce high efficiency solute partitioning in two-phase solvent systems. These systems generally use a stationary phase which is retained in the column while the mobile phase elutes through the system. In these prior systems, since the sample solution is introduced at the beginning of each operation, such systems are regarded as constituting batch separation techniques, and not continuous extraction processes.
However, continuous extraction processes necessitate "genuine" countercurrent flow, wherein two immiscible solvents move in opposite directions with respect to the separation column to allow continuous sample feeding and continuous enrichment and/or stripping of the ingredient or ingredients desired to be collected, present in a large quantity of liquid. Heretofore no satisfactory system for accomplishing this objective has been available.
The following prior U.S. Pat. Nos. illustrate the present state of the art:
Ito et al., 3,775,309 PA1 Ito et al., 4,040,742 PA1 Ito, 4,051,025 PA1 Ito, 4,058,460